The present invention related generally to porous ceramic substrates useful for filtration and/or high temperature chemical reaction processing, such as a catalytic host. The invention more particularly relates to a substantially biosoluble fiber-based ceramic substrate and methods for producing the same.
Ceramic honeycomb substrates are commonly used in industrial automotive applications where inherent material stability and structural integrity are needed at elevated operating temperatures. Ceramic honeycomb substrates provide high specific surface area for effective filtration and support for efficient catalytic reactions. For example, in automotive applications, ceramic substrates are used in catalytic converters to host catalytic oxidation and reduction of exhaust gases, and to filter particulate emissions.
Fiber-based ceramic substrates can be produced to provide a highly porous yet chemically and mechanically durable substrate for high temperature applications. Commonly owned U.S. Pat. No. 6,946,013, and commonly-owned U.S. patent application Ser. Nos. 11/323,429 filed Dec. 30, 2005, Ser. No. 11/322,777 filed Dec. 30, 2005, and Ser. No. 11/323,430 filed Dec. 30, 2005, all incorporated by reference herein, describe various methods and applications for highly porous fiber-based substrates. The raw materials used to fabricate such substrates may be subject to regulations in some jurisdictions that require special handling and/or hazardous product labeling. To avoid the effect of regulatory controls, and to minimize the potential for exposure to potentially hazardous materials by those involved in the manufacture of such substrates, ceramic fibers having compositions that are deemed to be biosoluble, i.e., soluble within a human or living organism, can be used.
Biosoluble fibers have been developed for use as a replacement for refractory ceramic fibers. These fibers can be exonerated from classification as a hazardous material, under currently-known regulatory directives. These biosoluble replacements are typically intended for insulation and refractory applications, where strength and chemical durability is not a primary concern. However, when implemented as the primary constituent in a porous ceramic substrate for high temperature filtration and/or chemical reaction processing using known methods of fabrication, the reduced strength and durability of these fibers detracts from the performance of the substrate in intended applications.
Accordingly, there is a need for a biosoluble fiber-based ceramic substrate that can be manufactured using methods to produce a substrate that provide sufficient strength and durability for high temperature filtration and/or chemical reaction processing.